Color flat panel displays, such as liquid crystal displays and the like, typically incorporate color filters used to provide pixels with color. One technique for fabricating color filters involves a laser-induced thermal transfer process. A particular prior art thermal transfer process is illustrated schematically in FIG. 1. A substrate 10, known in the art as a receiver element, is overlaid with a donor element 12, known in the art as a donor sheet. Donor element 12 typically incorporates a support layer 12A and a transfer layer 12B. Transfer layer 12B can include various transferable donor materials including colorants, pigments, or the like. Support layer 12A is typically made of plastic.
Donor element 12 is image-wise exposed to cause selected portions of transfer layer 12B to be transferred from support layer 12A to a surface of substrate 10. Some exposure methods employ one or more controllable lasers 14 to provide one or more corresponding laser beams 16 to induce the transfer of donor material from the imaged regions of donor element 12 to corresponding regions of substrate 10. Controllable laser(s) 14 may comprise diode laser(s) which are relatively easy to modulate, are relatively low cost, and are relatively small in size. Such laser(s) 14 are controllable to directly expose donor element 12. In some applications, masks (not shown) are used in exposing various media.
In some imaging applications, a number of different donor elements 12 are sequentially applied to substrate 10, imaged and then removed. For example, during typical fabrication of color filters, a first donor element 12 is used to apply one color, such as a red donor material to substrate 10, and the first donor element is then removed; a second donor element 12 is used to apply, for example, green donor material, and the second donor element is then removed; a third donor element 12 is used to apply, for example, blue donor material, and the third donor element is then removed.
Media loaders employing various cylindrical supports such as rollers and the like are typically employed to apply and/or remove flexible media such as donor element 12 to, or from various surfaces. The various rollers are employed in various operations which include but are not limited to: transferring and loading of media into the loader; application of media onto a surface; and removal of media from the surface after it has undergone a processing step (e.g. exposure). In some processes, the media is stored on media rolls and a web of the media is transferred from a media roll to a roller of the media loader during a loading operation. The loading operation can involve separating the media web into sheets of media. Wrinkles in the media can arise for various reasons. For example, mis-alignment between the media roll and the roller can lead to a non-uniform web tension which can cause wrinkles to form during loading. The difficulties associated with the loading operation can be further compounded when media is loaded from a plurality of media rolls (e.g. different colored donor elements) and each of the media rolls has a different orientation with respect to the roller sufficient to alter the web tension between the different loadings.
Exposure processes such as thermal transfer processes are typically sensitive to the uniformity of the interface between the applied donor element 12 and a substrate 10. Entrapped bubbles, wrinkles and the like can cause variances in the amount of donor material that is transferred to substrate 10 which can lead to various undesired image artifacts. Media that has been loaded into the media loader typically needs to be applied to substrate 10 such that a uniform interface free of wrinkles, bubbles, etc is created between the donor element 12 and substrate 10. Donor element 12 can be mounted onto the surface of a roller of the media loader (e.g. an application roller), and the roller can then be operated to apply the mounted donor element 12 to substrate 10. Mounted donor element 12 can be applied to substrate 10 by rolling the donor element 12 onto substrate 10. The present inventors have observed that if wrinkles or bubbles are entrapped between the donor element 12 and the application roller during the initial application of donor element 12 onto the application roller, entrapped wrinkles or bubbles are also likely to occur between the donor element 12 and substrate 10 during a subsequent application of donor element 12 to substrate 10. The present inventors have observed that wrinkles or bubbles are especially likely to occur if donor elements 12 with reduced calipers or thicknesses are employed.
There is need in the art for an imaging device that includes a media loader having an application roller onto which media can be loaded onto a surface thereof with reduced occurrences of entrapped wrinkles or bubbles.
There is need in the art for a thermal transfer imaging device that includes a media loader having an application roller onto which thermal transfer donor media can be loaded onto a surface thereof with reduced occurrences of entrapped wrinkles or bubbles.
There is a need in the art for a thermal transfer imaging device that includes a media loader having an application roller onto which thermal transfer donor media of reduced thicknesses can be loaded onto a surface thereof with reduced occurrences of entrapped wrinkles or bubbles.